Method of separating acenaphthene, diphenylene oxide and fluorene from aromatic oils



Claude E. Bole, Pittsburgh, and Kenneth A. Schowalter,

' Verona, Pa., assignors to United States Steel Corporation, a corporation of New Jersey Filed June 15, 1954, Ser. No. 436,862

3 Claims. (Cl. 202-71) This invention relates to a method of separating acenaphthene, diphenyleneoxide and fiuorene fromaro; matic or partially aromatic oils boiling over the=range of approximately 260 to 300 C. Such oils maybe obtained from coal hydrogenation or petroleum reforming and the invention is particularly suitable for separating such components from coal-tar or other fractions such as creosote oil. To the best of our knowledge it has not been possible to recover all three of the above named compounds from such oils by any single process. Processes used to recover any one or two of the three compounds are based upon fractional distillation, crystallization and solvent washing. These processes have the disadvantages of being complex, costly and inefficient.

It is therefore an object of our invention to provide a simple, inexpensive and efficient process for the separation and recovery of acenaphthene, diphenylene oxide and fluorene from coal-tar or other fractions containing these three ingredients. p p

This and other objects will be more apparent after referring to the following specification and attached drawing, in which the single figure is a schematic view of apparatus suitable for carrying out our method.

Referring more particularly to the drawing, reference numeral 2 indicates a distillation :unit to which coal-tar fractions or the like containing acenaphthene, diphenylene oxide and fiuorene are fed through a conduit 4. Recycle oil boiling over the range of approximately 260 to 300 C. is also delivered to the distillation unit 2 through a conduit 6. The distillation unit 2 is connected to a header 8 having four branch conduits 10, 12, 14 and 16 connected thereto. The conduits 10, -12, 14 and '16 are connected to tanks 18, 20, 22 and 24, respectively. Flow of material to the tanks-18, 20, 22 and 24 is controlled by means'of valves- 26, 28, 30 and 32 located in the conduits 10, 12, 14 and 16, respectively. Suitable means such as a valve outlet 33 may be provided to drain off material from tank 18. Tanks 20, 22 and 24 are connected to a heat exchanger 34 by means of conduits 36, 38 and 40, respectively. Valves 42, 44 and 46 are located in the conduits 36, 38 and 40, respectively, to control the flow therethrough. Heat exchanger 34 is connected to a centrifuge 48 by means of a conduit 50. Centrifuge 48 is connected by means of conduit 51 to a recycle oil storage tank 52 and to a product container 54 by means of a conduit 56. The tank 52 is con nected by means of the conduit 6 to the distillation unit 2. The tank 52 is also provided with conduit 58 having a valve 60 therein.

The operation of our method is as follows:

The oil to be processed and recycle oil boiling over the range of approximately 260 to 303 C. are fed to the still 2 through the conduits 4 and 6 and are distilled therein, the distillate being removed through the header 8. We have found that by adding such recycle oil until the total weight thereof in the mixture is at least three times the combined weight of the acenaphthene, diphenylene oxide and fluorene, each of these last named Patented Sept. 20, 1960 compounds will distill in a relatively narrow range below and at the boiling point of the pure compound as compared to the broad range in the original mixture. For economic operation the ratio should not exceed twenty to one and for best operation the ratio is approximately five to one. It is preferred to have the ratio greater when one of thecompounds is present in greater amounts than the other two. Initially valve 26 is open and valves 28, 30 and 32 closed. When a vapor temperature of approximately 265 C. (264268) is reached, valve 26 is closed and valve 28 opened. When a temperature of approximately 279 C. (278-280) is reached, valve 28 is closed and valve 30 opened and when a temperature of approximately 288 C. (287 -289) is reached, valve 30' is closed and valve 32 opened. When a vapor temperature reaches approximately 299 C. (298300) the distillation is discontinued. Thus the fraction distilling in the range of approxiamtely 265 to 279 C. is collected in tank 20, the fraction distillingin the range of approximately 279 to 288 C. is collectedin tank 22 and the fraction distilling in a range of approximately-288 to 299 C. is collected in tank 24. These distillation fractions are then processed individually to recover the crystalline solids in the following manner. Valve 42 is first opened and the distillate in tank 20 passes through the heat exchanger 34 where it is cooled to a temperature where the solids will crystallize, this temperature being approximately between zero and 45 C. and preferably about 20. C. The cooleddistillate then passes into the centrifuge 48 where it is separated into oil and the crystal solids. The oil will pass through conduit 51 totank 52and the solids into the container 54. This solid is acenaphthene substantially free of diphenylene oxide and fluorene. The distillate fractions from tanks 22 and 24 are processed in a similar manner and yield commercially pure diphenylene oxide and fluorene, respectively.

The original recycle oil may be obtained as follows. A coal-tar fraction of the type described is distilled in the still 2 and the three fractions distilling in the ranges of approximately 265 to 284 '01, approximately 284 to 291 cfand approxirnately 291 to 303 C. are collected separately in tanks 20, 22'and 24. These distillation fractions are then processed individually in substantially the same manner as described above, that is, they are individually cooled in the heatexchanger 34 and the crystals separated from the oil in the centrifuge 48. The crystalline fraction from tank 20 consists mainly of acenaphthene with appreciable amounts of diphenylene oxide and fiuorene. The crystalline fractiori'frorn tank 22 consists principally of diphenylene oxide but also contains appreciable amounts of acenaphthene and fluorene. The crystalline fraction from tank 24 is mostly fluorene with an appreciable amount of diphenylene oxide present. The oil fractions from all of these fractions are collected in the tank 52 as the recycle oil. Such oil will contain the quantities of acenaphthene, diphenylene oxide and fluorene which are soluble in the oil at the temperature of crystallization. While the method described above is preferred because of its efliciency, the oil fractions originally obtained can be mixed and the mixture distilled with the fractions distilling in the ranges of approximately 265 to 279 0., approximately 279 to 288 C. and approximately 288 to 299 C. being collected separately in the tanks 20, 22 and 24.

Also, if desired, proportionate parts of the crystal fractions originally collected from tanks 20, 22 and 24 may be added to the oil fractions in tank 52 with the total amount of such additions not exceeding one-fifth the weight of the oil fractions. This mixture can then be distilled, cooled and filtered in the manner described above to obtain acenaphthene, diphenylene oxide and fluorene in commercially pure form.

Another modification of our process is as follows. Creosote oil or coal-tar fractions containing acenaphthene, diphenylene oxide and fluorene is distilled into four fractions. With creosote oil containing approximately 1.5% 'acenaphthene, 1.7% diphenylene oxide and 3.4% fluorene, the boiling ranges of these four fractions are approximately 265 to 279 C., approximately 279 to 288 C., approximately 288 to 295 C. and approximately 295 to 300 C. The first fraction will be crude acenaphthene, the second crude diphenylene oxide, the third crude fluorene and the fourth commercially pure fluorene amounting to about 60% of the total fluorene present in the raw material. These fractions are separate ly cooled to between and 45 C., preferably to 20 C., and filtered to separate the crystalline solids. The combined oils from the filtration of the four fractions are added to the mixture of the crystalline solids from the first three fractions in an amount of about one part solids to four parts of oil by weight. This mixture is then distilled into the three fractions distilling in the ranges of approximately 265 to 279 C., 279 to 288 C. and 288 to 299 C. and the fractions separately collected and filtered in the manner described above.

It will be understood that the crystals may be separated from the oil by other methods such as by filtration. The methods employed may be either of the batch or continuous type. v

In each of the methods described above, it will be seen that the product finally distilled is a mixture of the solids acenaphthene, diphenylene oxide and fluorene with aromatic or partially aromatic oils boiling over the temperature range of 260 to 303 C. with the amount of oil be ing at least three times the combined weight of the solids.

While several embodiments of our invention have been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

We claim:

1. The method of separating acenaphthene, diphenylene oxide and fluorene from a coal-tar fraction or the like containing the same which comprises adding a coaltar recycle oil distilled over the range of 260 to 303 C. to the said coal-tar fraction in the ratio of between three and twenty times the total weight of acenaphthene, diphenylene oxide and fluorene in the said coal-tar fraction, fractionally distilling the mixture of coal-tar fraction and oil, separately collecting the fractions distilled in the ranges of approximately 265 to 279 0., approximately 279 to 288 C. and approximately 288 to 299 C., cooling said last named fractions until crystals of the solids form, separating the crystals formed upon cooling from the oil of the fractions to obtain acenaphthene, di-

phenylene oxide and fluorene each substantially free of the other two compounds.

2. The method of obtaining acenaphthene, diphenylene oxide and fluorene from a coal-tar fraction or the like containing the same which comprises fractionally distilling a portion of said coal-tar fraction, separately collectin-g the fractions distilled in the ranges of approxi mately 265 to 284 C., approximately 284 to 291 C. and approximately 291 to 303 C., cooling said fractions to a temperature of between 0 and 45 C., separating the crystals formed upon cooling from the oil of the fractions, adding the said oil fractions to a portion of said coal-tar fraction in the ratio of between three and twenty times the total weight of acenaphthene, diphenylene oxide and fluorene in the last named portion of said coal-tar fraction, fractionally distilling the mixture of coal-tar fraction and oil, separately collecting the fractions distilled in the ranges of approximately 265 to 279 C., approximately 279 to 288 C. and approximately 288 to 299 C., cooling said last named fractions to a temperature of between 0 and 45 C., and separating the crystals formed upon cooling from the oil of the fractions to obtain acenaphthene, diphenylene oxide and fluorene each substantially free of the other two compounds.

3. The method of obtaining acenaphthene, diphenylene oxideand fluorene from a coal-tar fraction or the like containing the same which comprises fractionally distilling said coal-tar fraction, separately collecting the fractions distilled in the ranges of approximately 265 to 279 C., approximately 279 to 288 0., approximately 288 to 295 C. and approximately 295 to 300 C., cooling said last named fractions until crystals of the solids form, separating the crystals formed upon cooling from the oil of the fractions, mixing the oils from all the fractions to the solids from the first three fractions in such amounts that the weight of said oil is at least three times the combined weight of the acenaphthene, diphenylene oxide and fluorene, fractionally distilling the last named mixture, separately collecting the fractions distilled in the ranges of approximately 265 to 279 C., approximately 279 to 288 C. and approximately 288 to 299 C., cooling. said last named fractions until crystals of the solids form, and separating the crystals formed upon cooling from the oil of the fractions to obtain acenaphthene, diphenylene oxide and fluorene each substantially free of the other two compounds.

Smith Jan. 14, 1930 Sokol Mar. 29, 1949 

1. THE METHOD OF SEPARATING ACENAPHTHENE, DIPHENYLENE OXIDE AND FLUORENE FROM A COAL-TAR FRACTION OR THE LIKE CONTAINING THE SAME WHICH COMPRISES ADDING A COALTAR RECYCLE OIL DISTILLED OVER THE RANGE OF 260 TO 303* C. TO THE SAID COAL-TAR FRACTION IN THE RATION OF BETWEEN THREE AND TWENTY TIMES THE TOTAL WEIGHT OF ACENAPHTHENE, DIPHENYLENE OXIDE AND FLUORENE IN THE SAID COAL-TAR FRACTION, FRACTIONALLY DISTILLING THE MIXTURE OF COAL-TAR FRACTION AND 